Appraising the Dimensionality of the Medical College Admission Test. MCAT Monograph.

To provide a better understanding of the structure of the Medical College Admission Test (MCAT) and to determine if there are structural differences across selected groups of MCAT examinees, several dimensionality analyses were conducted on data from recent administrations of the MCAT. The first set of analyses focused on the global structure of the MCAT, and the second set appraised the consistency of the structure of data across groups of testtakers that differed with respect to sex, repeater/nonrepeater status, orientation to the English language, and race/ethnicity. Data from two forms of the MCAT were used. Forms 15A and 15B were administered in 1994 to 16,520 examinees, and Forms 23A and 23B were administered in 1996 to 12,625 examinees. Results suggest that appraisals of the MCAT structure should be conducted at the parcel level rather than at the item level. Parcel-level results suggest that a dominant factor underlies the MCAT. This is probably a "general intelligence" factor. The results also suggest additional factors that represent the principal disciplines measured on the MCAT. After the general factor, the next structural layer of the MCAT separates test material measuring science from test material measuring verbal reasoning and writing skills. The next structural level depicts three factors: science, verbal reasoning, and writing skills. These three factors were supported by all analyses. Results also support the distinction between the science disciplines, and, in general, analyses support the current content structure of the MCAT reported in the test blueprint. From a statistical perspective, results suggest it might be possible to scale the biological and physical sciences along a single continuum. With respect to the consistency of the MCAT structure across selected groups of testtakers, results supported the hypothesis of structural invariance across groups. In general, multidimensional scaling analyses indicated that all dimensions were relevant for accounting for the variation in the data for each group. Some exceptions are discussed. An appendix contains depictions of the confirmatory factor analysis models and parceling schemes. (Contains 13 figures, 30 tables, and 20 references.) (SLD)